The goal of this project is to understand the process by which the pathogenic bacterium Pseudomonas aeruginosa kills the nematode worm Caenorhabditis elegans. C. elegans has recently been developed as a host model for a number of pathogens. Work in the Ausubel laboratory has shown that the molecular responses to pathogens in the worm are similar to those in other organisms, including humans. Preliminary work has demonstrated that low molecular weight toxins secreted by P. aeruginosa are responsible for the rapid killing of C. elegans. The specific aims of this project are: 1. Identification and isolation of compounds required for fast killing of C. elegans by P. aeruginosa a. Identification of toxins by discovery metabolite profiling (DMP) of fast-killing vs. fast-killing defective mutant P. aeruginosa b. Chromatographic purification and testing of potential fast-killing toxins 2. Characterization of mechanism of action of fast killing toxins a. Detection of activation of known C. elegans immune pathways by toxins and localization b. Determination of effects of toxins on host transcriptional response c. Measurement of the effects on pathogenesis of host transcriptional responses to toxin(s). PUBLIC HEALTH RELEVANCE: The proliferation of antibiotic-resistant bacterial pathogens poses a serious threat to human health. Understanding the chemical mechanisms of pathogenesis is a key step in the development of a novel class of antimicrobial drugs that inhibit pathogenesis.